Some inspiration, with French Foreign Legion :




Here you have mine :

For the colors :
beige : GW Steel Legion drab, with black for shadows and highlights by adding GW karak stone (you can try with other colors, as it's a beige slitghtly green). Maybe you can try with PA kaki n°988
brown spots : GW dryad bark, highlights with Prince August heavy sienna (G154)
green spots : Prince August "military green" (n°975), highlighted by adding PA ivory (n°918)
black spots are black and highlighted with PA ivory.
For backpacks, you can paint them the same way as clothes, or in plane brown with PA english uniform n°921, shadows by adding black and highlights with PA ivory. But it seems too bright and I think I will rework them to be in a more fadded beige, nearly the same of the F3 uniform, just as I must rework the dust googles on the helmet (less orange, more smocky black).
The flackjacket (CIRAS, for googling pics) seems to be plane brown or light green.
Just a little details : legs of trousers are wrong on the Empress minis. They based themselves on the FELIN uniform (same for the helmet), but now the F3 uniform actually weared has different form of trousers.
But it's important only if you are a fan of those details as those minis are really nice.